U.S. patent application number 11/256102 was filed with the patent office on 2006-04-27 for gaseous fuel injector.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Kenji Date, Masaaki Kato.
Application Number | 20060086825 11/256102 |
Document ID | / |
Family ID | 36205326 |
Filed Date | 2006-04-27 |
United States Patent
Application |
20060086825 |
Kind Code |
A1 |
Date; Kenji ; et
al. |
April 27, 2006 |
Gaseous fuel injector
Abstract
The injector includes a nozzle, a needle, a control chamber, a
working fluid supply passage, an electric switching valve, a
high-pressure gaseous fuel supply passage and a lubrication liquid
fuel supply passage. The nozzle has an injection hole, through
which high-pressure gaseous fuel is injected. The needle is axially
reciprocably received in the nozzle to open and close the injection
hole. The needle includes a sliding portion and a valve portion.
The control chamber applies a pressure to the needle. The working
fluid supply passage supplies liquid fuel to the control chamber.
The electric switching valve controls an inflow/outflow of the
liquid fuel to/from the control chamber. The high-pressure gaseous
fuel supply passage supplies the high-pressure gaseous fuel to the
injection hole. The lubrication liquid fuel supply passage supplies
the liquid fuel from the working fluid supply passage to the
sliding portion and the valve portion.
Inventors: |
Date; Kenji; (Obu-city,
JP) ; Kato; Masaaki; (Kariya-city, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
36205326 |
Appl. No.: |
11/256102 |
Filed: |
October 24, 2005 |
Current U.S.
Class: |
239/408 |
Current CPC
Class: |
F02M 21/0263 20130101;
Y02T 10/30 20130101; Y02T 10/32 20130101; F02M 21/0254 20130101;
F02M 43/04 20130101; F02D 19/0647 20130101; Y02T 10/36 20130101;
F02D 19/0694 20130101; F02M 61/042 20130101 |
Class at
Publication: |
239/408 |
International
Class: |
B05B 7/12 20060101
B05B007/12 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 25, 2004 |
JP |
2004-309175 |
Claims
1. An injector for an internal combustion engine, the injector
comprising: a nozzle that has an injection hole, through which
high-pressure gaseous fuel is injected into a combustion chamber of
the engine; a needle that is axially reciprocably received in the
nozzle to open and close the injection hole of the nozzle, wherein:
the needle includes a sliding portion and a valve portion; the
valve portion closes the injection hole when the valve portion
engages an inner surface of the nozzle; and the sliding portion and
the valve portion are exposed to the high-pressure gaseous fuel; a
control chamber for applying a pressure to the needle; a working
fluid supply passage for supplying liquid fuel, which serves as a
working fluid, to the control chamber; an electric switching valve
for controlling an inflow of the liquid fuel to the control chamber
and an outflow of the liquid fuel from the control chamber; a
high-pressure gaseous fuel supply passage for supplying the
high-pressure gaseous fuel to the injection hole; and a lubrication
liquid fuel supply passage for supplying the liquid fuel, which
serves as a lubrication, from the working fluid supply passage to
the sliding portion and the valve portion of the needle.
2. The injector according to claim 1, wherein: the sliding portion
of the needle includes a guide portion; the nozzle includes a slide
hole, which slidably receives the guide portion; the valve portion
of the needle includes a seating part; the lubrication liquid fuel
supply passage includes: a first lubrication liquid fuel supply
passage, which communicates with the working fluid supply passage
at a first end, wherein a second end of the first lubrication
liquid fuel supply passage opens at the slide hole; and a second
lubrication liquid fuel supply passage, which is located inside the
needle, wherein: a first end of the second lubrication liquid fuel
supply passage opens at an outer peripheral surface of the guide
portion to communicate with the first lubrication liquid fuel
supply passage; and a second end of the second lubrication liquid
fuel supply passage opens at an upstream side of the seating part
of the needle.
3. The injector according to claim 2, wherein the second
lubrication liquid fuel supply passage is constructed such that the
first end of the second lubrication liquid fuel supply passage is
communicated and discommunicated relative to the first lubrication
liquid fuel supply passage through opening and closing the
injection hole by the needle.
4. The injector according to claim 3, wherein: the first end of the
second lubrication liquid fuel supply passage and the second end of
the first lubrication liquid supply passage are communicated with
each other when the needle is placed in a communicating position;
and the first end of the second lubrication liquid fuel supply
passage and the second end of the first lubrication liquid supply
passage are discommunicated from each other when the needle is
placed in spaced away from the communicating position.
5. The injector according to claim 3, wherein the needle includes a
circumferential groove, which is located in the upstream side of
the seating part, and the second end of the second lubrication
liquid fuel supply passage opens at the circumferential groove.
6. An injector for an internal combustion engine, the injector
comprising: a nozzle that has an injection hole, through which
high-pressure gaseous fuel is injected into a combustion chamber of
the engine; a needle that is axially reciprocably received in the
nozzle to open and close the injection hole of the nozzle; a
control chamber for applying a pressure to the needle; a working
fluid supply passage for supplying liquid fuel, which serves as a
working fluid, to the control chamber; an electric switching valve
for controlling an inflow of the liquid fuel to the control chamber
and an outflow of the liquid fuel from the control chamber; a
high-pressure gaseous fuel supply passage for supplying the
high-pressure gaseous fuel to the injection hole; and an ignition
facilitating liquid fuel supply passage for supplying the liquid
fuel, which facilitates an ignition, from the working fluid supply
passage to the high-pressure gaseous fuel supply passage that is
located in a distal end portion of the nozzle, wherein the liquid
fuel is injected along with the high-pressure gaseous fuel in a
case where the injection hole is opened.
7. The injector according to claim 6, wherein: the needle includes
a seating part; the ignition facilitating liquid fuel supply
passage is located inside the needle; a first end of the ignition
facilitating liquid fuel supply passage communicates with the
working fluid supply passage; a second end of the ignition
facilitating liquid fuel supply passage opens near the seating part
of the needle; and the liquid fuel, which facilitates the ignition,
is injected by use of an energy of a flow of the high-pressure
gaseous fuel flowing toward the injection hole.
8. The injector according to claim 7, wherein the needle includes a
guide portion, the injector further comprising a lubrication liquid
fuel supply passage for supplying the liquid fuel, which serves as
a lubrication, from the working fluid supply passage to the guide
portion of the needle, wherein the first end of the ignition
facilitating liquid fuel passage opens at the guide portion of the
needle to communicate with the working fluid supply passage through
the lubrication liquid fuel supply passage.
9. The injector according to claim 8, wherein the needle includes a
circumferential groove, which is located in a downstream side of
the seating part, wherein the second end of the ignition
facilitating liquid fuel supply passage opens at the
circumferential groove.
10. The injector according to claim 8, wherein: the lubrication
liquid fuel supply passage is a first lubrication liquid fuel
supply passage; the nozzle includes a slide hole, which slidably
receives the guide portion of the needle; and the ignition
facilitating liquid fuel supply passage is a common inside-needle
fuel passage, which commonly supplies the liquid fuel both to serve
as the lubrication and to facilitate the ignition, the injector
further comprising a second lubrication liquid fuel supply passage,
which is located inside the needle, wherein: the first end of the
first lubrication liquid fuel supply passage communicates with the
working fluid supply passage; the second end of the first
lubrication liquid fuel supply passage opens at the slide hole,
which slidably receives the guide portion of the needle; a first
end of the second lubrication liquid fuel supply passage
communicates with the second end of the first lubrication liquid
fuel supply passage through the common inside-needle fuel passage;
and a second end of the second lubrication liquid fuel supply
passage opens at an upstream side of the seating part of the
needle.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on and incorporates herein by
reference Japanese Patent Applications No. 2004-309175, filed on
Oct. 25, 2004.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a gaseous fuel injector,
which directly injects a high-pressure gaseous fuel to cylinders of
an internal combustion engine.
[0004] 2. Description of Related Art
[0005] In development of a next generation vehicle, a clean exhaust
gas and a decrease of carbon dioxide are greatly required. However,
conventional combustion technology using liquid fossil fuel may not
reach this requirement. Development of a gaseous fuel engine using
gas fossil fuels and hydrogen gas as alternative fuels for the
liquid fossil fuel is progressing and some of the gaseous fuel
engines are actually used. Here, the gas fossil fuels, which
expectedly contribute effective combustion, include a natural gas
and a petroleum gas.
[0006] A cylinder direct injection engine may not be used long in a
case where a conventional gaseous fuel is used, because the
conventional gaseous fuel has low lubricity. Thus, there may be
reliability disadvantages, such as wear and burn-in of a nozzle
sliding portion of the injector, and sealing failure caused by the
wear of a valve portion. Also a compression ignition engine may
have a disadvantage, such as an unstable operation with the gaseous
fuels (e.g., the hydrogen gas and the natural gas, which have low
cetane numbers).
[0007] To improve reliability and operational performance, several
techniques are proposed (see Unexamined Japanese Patent Publication
No. 2003-232234 and Unexamined Japanese Utility Model Publications
No. S63-4365 and No. H1-88054).
[0008] Unexamined Japanese Patent Publication No. 2003-232234
discloses a two-fuel injection technique, which supplies either or
both of the gaseous fuel (e.g., LPG) and the liquid fuel (e.g.,
gasoline) from corresponding injectors based on a state of an
engine operation. According to the technique, the first fuel supply
system, which supplies the gaseous fuel from the first injector,
and the second fuel supply system, which supplies the liquid fuel
from the second injector, are provided. In a transition from an
operational state using the liquid fuel to an operational state
using only the gaseous fuel, the first and second injectors
simultaneously supply the gaseous fuel and the liquid fuel to the
internal combustion engine to avoid an excessive lean state of an
air fuel ratio. Thus, misfire or deterioration of the operational
performance is limited.
[0009] Unexamined Japanese Utility Model Publications No. S63-4365
discloses a gas injector for injecting gas supplied from an
accumulator to lubricate the sliding portion of the needle by a
seal oil, which is supplied to the injector through an additionally
provided passage to seal the needle portion. The gas injector also
includes an inlet passage for supplying a working fluid to open and
close a valve portion. Unexamined Japanese Utility Model
Publication No. H1-88054 discloses an injector that has an improved
lubricity of the needle by using the working fluid as a lubrication
and storing the working fluid and the gaseous fuel in a seal oil
storage.
[0010] In practice, the technique of Unexamined Japanese Patent
Publication No. 2003-232234 largely depends on the liquid fuel to
operate the engine in order to limit an evaporation of the liquid
gaseous fuel. Thus, an effect of using the gaseous fuel may not be
maximized. Also, an apparatus of the invention may become large,
because the technique requires two large fuel tanks for the gas
liquid and the liquid fuel, and also requires two fuel supply
systems and two fuel injector valves for the two fuel tanks.
[0011] In the invention according to Unexamined Japanese Utility
Model Publication No. S63-4365, the composition of the technique
may be complex, because the seal oil, as well as the working fluid
that drives the injector, is also supplied to the injector.
Moreover, the seal oil may continuously leak into the working fluid
and the gaseous fuel, because a pressure of the seal oil is applied
to a seal groove of the needle. In the invention according to
Unexamined Japanese Utility Model Publication No. H1-88054, a lower
portion of the needle is not lubricated sufficiently, because the
working fluid does not easily reach a lower portion (or an
injection hole side) of the seal oil storage due to pressure of the
gaseous fuel, which is applied therein. Also, the inventions
according to Unexamined Japanese Utility Model Publications No.
S63-4365 and No. H1-88054 are not effective for decreasing wear of
the valve portion, because both inventions improve the lubricity of
only the sliding portion of the needle.
SUMMARY OF THE INVENTION
[0012] The present invention addresses the above disadvantages.
Thus, it is an objective of the present invention to provide an
injector that mainly injects a high-pressure gaseous fuel, has
limited wear and bum-in, and has an improved reliability. It is
also an objective of the present invention to provide an injector
with an improved ignition performance in injecting the
high-pressure gaseous fuel to realize a stable operation.
[0013] To achieve the objective of the present invention, there is
provided an injector for an internal combustion engine. The
injector includes a nozzle, a needle, a control chamber, a working
fluid supply passage, an electric switching valve, a high-pressure
gaseous fuel supply passage and a lubrication liquid fuel supply
passage. The nozzle has an injection hole, through which
high-pressure gaseous fuel is injected into a combustion chamber of
the engine. The needle is axially reciprocably received in the
nozzle to open and close the injection hole of the nozzle. The
needle includes a sliding portion and a valve portion. The valve
portion closes the injection hole when the valve portion engages an
inner surface of the nozzle. The sliding portion and the valve
portion are exposed to the high-pressure gaseous fuel. The control
chamber applies a pressure to the needle. The working fluid supply
passage supplies liquid fuel, which serves as a working fluid, to
the control chamber. The electric switching valve controls an
inflow of the liquid fuel to the control chamber and an outflow of
the liquid fuel from the control chamber. The high-pressure gaseous
fuel supply passage supplies the high-pressure gaseous fuel to the
injection hole. The lubrication liquid fuel supply passage supplies
the liquid fuel, which serves as a lubrication, from the working
fluid supply passage to the sliding portion and the valve portion
of the needle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The invention, together with additional objectives, features
and advantages thereof, will be best understood from the following
description, the appended claims and the accompanying drawings in
which:
[0015] FIG. 1A is a sectional view of a main portion of an injector
showing a structure of a nozzle of the injector according to a
first embodiment of a present invention;
[0016] FIG. 1B is an enlarged view of a part I B in FIG. 1A showing
a lower end portion of the nozzle;
[0017] FIG. 2 is a schematic view taken along line II-II in FIG. 4
showing a supply passage of a high-pressure gaseous fuel of the
injector according to the first embodiment;
[0018] FIG. 3 is a schematic view taken along line III-III in FIG.
4 showing the supply passage of a working fluid of the injector
according to the first embodiment;
[0019] FIG. 4 is a top view of the injector viewed from a direction
IV in FIG. 2 according to the first embodiment;
[0020] FIG. 5 is a sectional view of the nozzle structure of the
injector according to a second embodiment of the present invention;
and
[0021] FIG. 6 is an enlarged view of a part VI in FIG. 5 showing
structure of a nozzle lower end portion.
DETAILED DESCRIPTION OF THE INVENTION
(First Embodiment)
[0022] A first embodiment of a present invention will be described
with reference to FIGS. 1A to 4. Injectors 1 according to the first
embodiment, directly inject a high-pressure gaseous fuel to
cylinders of the multi-cylinder compression ignition engine. Each
combustion chamber of the cylinder has the corresponding injector
1.
[0023] FIGS. 2 and 3 are longitudinal sectional views of the
injector 1 according to the present embodiment. FIG. 1B is an
enlarged view of a nozzle 3, which is a main part of the injector 1
according to the present embodiment. FIG. 2 describes a
distribution passage of a working fluid, which is supplied to a
control chamber 2 to drive the nozzle 3. FIG. 3 describes a supply
passage of a high-pressure gaseous fuel, which is injected from the
nozzle 3. A hydrogen fuel may serve as the high-pressure gaseous
fuel. A liquid fuel, such as a light oil, serves as the working
fuel. FIG. 4 is a plan view of the injector 1, which is a view from
a direction indicated by IV in FIG. 2. FIG. 2 is a schematic view
taken along line II-II in FIG. 4. FIG. 3 is a schematic view taken
along line III-III in FIG. 4.
[0024] The present invention is characterized by using the liquid
fuel, which is different from high-pressure gaseous fuel (or
injection fuel) and serves as a working fluid for an on-off control
of pressure in the control chamber 2. A needle 31 is driven to a
closed position to close injection holes 37 by using pressure of
the liquid fuel in the control chamber 2 (FIG. 2). The needle 31 is
driven to an open position by using pressure of the high-pressure
gaseous fuel in a nozzle chamber 35 (FIG. 3). In the control
chamber 2, pressure is applied to drive the needle 31 to the closed
position to close the injection holes 37. The structure of the
control chamber 2 is known as a nozzle driving type for the liquid
fuel injector. The injector 1, which injects gaseous fuel, is
designed in the manner of this nozzle driving type to provide
supply passages for the liquid fuel and the high-pressure gaseous
fuel in one injector in order to control the injection.
[0025] In the present embodiment, a part of the liquid fuel, which
is supplied to control the pressure in the control chamber 2, is
supplied to a sliding portion to serve as a lubrication. Also, a
small portion of the liquid fuel is injected into an engine
combustion chamber along with the high-pressure gaseous fuel to
serve as an ignition facilitating fuel. Thus, the liquid fuel,
which is supplied as the working fluid, is effectively used to
improve the lubricity and ignitability performance, in which the
gaseous fuel injector may have disadvantages. A liquid fuel passage
constitution to realize the above-described advantages will be
described in detail later.
[0026] The ignitability performance is improved by injecting a
small amount of the light oil (the liquid fuel), which is more
liable to spontaneously ignite than a hydrogen gas (the gaseous
fuel).
[0027] The basic structure of the injector 1 and the distribution
passage of the working fluid will be described with reference to
FIG. 2. In FIG. 2, the injector 1 includes an injector body 5, a
nozzle 3 and a solenoid valve 6. The nozzle 3 is located at a lower
side of the injector body 5 in such a manner that a tip gasket 51
is inserted between the injector body 5 and the nozzle 3. The
solenoid valve 6, which serves as an electric switching valve, is
located at an upper open end of the injector body 5 in such a
manner that a plate member 21 is inserted between the solenoid
valve 6 and the injector body 5. The nozzle 3 and tip gasket 51 are
integrally fastened to the injector body 5 by using a retaining nut
33. The solenoid valve 6 is integrally fastened to the injector
body 5 by using a nut 62.
[0028] The injector body 5 is formed into a tubular shape. A
control piston 52 is slidably supported inside a tube hole of the
tubular injector body 5. The control chamber 2 is formed at an
upper end side of the control piston 52. In a tubular wall portion
of the injector body 5, two working fluid passages face with each
other in such a manner that the control piston 52 is located
between the two working fluid passages. The two working fluid
passages extend in a longitudinal direction (a vertical direction
in FIG. 2). One of the two working fluid passages is a first
high-pressure liquid passage 22. The other is a low-pressure fluid
return passage 25. The first high-pressure liquid passage 22
communicates with a liquid inlet pipe 23, which is obliquely
upwardly projected from an upper portion of the injector body 5.
Also, the first high-pressure liquid passage 22 is connected with a
liquid fuel common rail accumulator 27, which accumulates the
liquid fuel at a predetermined high pressure, through a liquid
supply pipe 28. The low-pressure liquid return passage 25
communicates with a liquid fuel tank (not shown) through a liquid
discharging pipe 26, which is upwardly projected from the upper
portion of the injector body 5.
[0029] The nozzle 3 slidably supports the stepped needle 31 inside
a vertical hole, which is formed in a nozzle body 32 to extend in
the longitudinal direction. An upper portion of the needle 31 is
connected with a lower portion of the control piston 52, and the
needle 31 vertically moves integrally with the control piston 52.
The needle 31 is biased downwardly by a return spring 53, which is
located in a spring chamber 54 that is located radially outwardly
of a lower end of the control piston 52. A lower end of the
high-pressure liquid passage 22 communicates with a second
high-pressure liquid passage 34, which is located in the nozzle
body 32. The second high-pressure liquid passage 34 opens around a
guide portion 311, which is a large diameter portion of the needle
31. A structure of the liquid fuel passage (or an inside-needle
fuel passage) inside the nozzle 3 is a characteristic feature of
the present invention and will be described later. A lower end of
the low-pressure liquid return passage 25 communicates with the
spring chamber 54 and a recovered leak oil from each member of the
injector flows through the low-pressure liquid return passage 25
and is discharged from a liquid discharge pipe 26.
[0030] The plate member 21 is located inside the upper open end of
the injector body 5 in such a manner that the plate member 21
closes an open end of the tube hole, in which the control piston 52
slides. The control chamber 2 is defined by an upper end surface of
the control piston 52, an inner wall of the tube hole above the
control piston 52 and a recess portion, which is located in a
center of a lower end surface of the plate portion 21. The control
chamber 2 normally communicates with a high-pressure passage 24,
which branches off the high-pressure liquid passage 22, through an
inlet throttle portion 2a. The pressure in the control chamber 2 is
applied downward to the needle 31 through the control piston 52.
The control chamber 2 also communicates with the low-pressure
liquid return passage 25 through an outlet throttle portion 2b. The
pressure in the control chamber 2 is controlled through the
solenoid valve 6, which controls the communication and
discommunicated between the control chamber 2 and the low-pressure
liquid return passage 25. The working fluid supply passage, which
includes the fluid inlet pipe 23, the first high-pressure liquid
passage 22, the high-pressure passage 24 and the inlet throttle
portion 2a, is connected to the control chamber 2.
[0031] The solenoid valve 6 includes a solenoid body 61, a tubular
solenoid 64 and a control valve 63. The tubular solenoid 64 is
received by the solenoid body 61. The control valve 63 includes an
armature and a ball valve. A cross section of the armature is
formed into a T-shape, and an upper end of the armature faces with
a lower end surface of the solenoid 64. The ball valve is supported
by a hemispheric concave portion, which is located at a lower end
portion of the armature. A low-pressure passage 65, which provides
communication between the outlet throttle portion 2b and the
low-pressure liquid return passage 25, is located around the lower
end portion of the armature. The control valve 63 is biased
downwardly by a spring 66, which is located inside the tubular
solenoid 64, when not energized so that the ball valve closes the
outlet throttle portion 2b of the control chamber 2.
[0032] FIG. 3 shows a supply passage of the high-pressure gaseous
fuel to the injection holes 37, which are formed at an end of the
nozzle 3. An annular space is defined by an inner peripheral wall
of a nozzle body 32 and a stem portion 312, which is a small
diameter portion of the needle 31, to form the nozzle chamber 35. A
suction chamber 39 is formed below the annular space. The injection
holes 37 are formed to penetrate through a wall, which forms the
suction chamber 39. Two gaseous fuel passages, which extend in the
longitudinal direction (the vertical direction in FIG. 3), are
formed in the tubular wall portion of the injector body 5. One of
the two gaseous fuel passages is a high-pressure gas passage 41 and
the other is a leak gas recovering passage 42. The high-pressure
gas passage 41 communicates with a high-pressure gas inlet pipe 44,
which is obliquely upwardly projected from the upper portion of the
injector body 5. The high-pressure gas passage 41 is connected to a
high-pressure gaseous fuel common rail accumulator 46 (or an
accumulator) through a high-pressure gas pipe 47 and a throttle 45.
The leak gas recovering passage 42 communicates with a gaseous fuel
tank (not shown) through an outlet 48, which is located at the
upper portion of the injector body 5. The high-pressure inlet pipe
44 is formed at an angle of 90.degree. from a projecting direction
of the liquid inlet pipe 23 as shown in FIG. 4. A high-pressure
gaseous fuel supply passage includes each passage, which provides
connection between the high-pressure inlet pipe 44 and the
injection holes 37.
[0033] It is desirable that a plurality of volume portions is
formed on a passage to inject a large amount of the gaseous fuel
with a low density in a short time. The passage is located between
the high-pressure inlet pipe 44 and the high-pressure gas passage
41. The plurality of volume portions sharply enlarges a
cross-section of the passage. The high-pressure gaseous fuel
passage is located between the high-pressure gaseous fuel common
rail accumulator 46 and the injection holes 37 of the injector 1.
In the present embodiment, a cavity is formed inside the thick
tubular wall portion, which is located along the passage to the
high-pressure gas passage 41, and serves as an injector chamber 43.
Also, the nozzle chamber 35 with a predetermined volume is formed
around the stem portion 312, which is located in upstream of the
injection holes 37, of the needle 31. The nozzle body 32 includes a
plurality of feed passages 36a, 36b, which are connected to a lower
end of the high-pressure gas passage 41, to effectively supply the
high-pressure gaseous fuel to the nozzle chamber 35. The feed
passages 36a, 36b make it possible to supply a large amount of
high-pressure gaseous fuel to the nozzle chamber 35.
[0034] When the solenoid 64 is supplied with a drive current based
on an opening command from a control device (not shown) to lift
(or, to open) the control valve 63 against a spring force of the
spring 66, the outlet throttle portion 2b of the control chamber 2
is opened. When the control valve 63 is opened, the high-pressure
fuel in the control chamber 2 is discharged to the low-pressure
liquid return passage 25 through the outlet throttle portion 2b and
the low pressure passage 65. The outlet throttle portion 2b
controls an amount of the high-pressure fuel supplied to the
low-pressure passage 65 from the control chamber 2. The inlet
throttle portion 2a controls an amount of the high-pressure fuel
supplied to the control chamber 2 from the high-pressure passage 24
shown in FIG. 2. At this time, a passage area of the outlet
throttle portion 2b is predetermined to be larger than that of the
inlet throttle portion 2a. Thus, the pressure in the control
chamber 2 is decreased by opening the control valve 63.
[0035] When the pressure in the control chamber 2 decreases, a
downward force, which downwardly pushes the control piston 52 and
the needle 31, is decreased. Thus, an upward force, which upwardly
pushes the needle 31, of the high-pressure gaseous fuel in the
nozzle chamber 35 becomes larger than a sum of downward forces,
which downwardly push the needle 31, of the spring 53 and the
decreased pressure of the liquid fuel in the control chamber 2.
When the needle 31 is lifted so that a seating part 38 is detached
from the nozzle body 32, the high-pressure gaseous fuel flows
through the suction chamber 39, and is injected into the engine
combustion chamber through the injection holes 37.
[0036] In the present invention as described above, the control
chamber 2 is provided to produce a large driving force in order to
effectively drive the needle 31. Here, the control chamber 2 serves
to apply back pressure to the needle 31. Also, the injector 1 is
structured to use the liquid fuel, which serves as the working
fluid, to drive the control piston 52.
[0037] A detailed structure of the nozzle 3 will be described with
reference to the enlarged view of the nozzle 3 shown in FIG. 1A. An
end portion of the needle 31 is formed into a generally inverted
cone shape. The needle 31 is biased downwardly by the pressure in
the control chamber 2 (FIG. 2) and the spring force of the spring
53 so that the seating part 38 pressingly contacts with an inner
peripheral surface, with which the seating part 38 faces, of the
nozzle body 32. At this time, the suction chamber 39, which is
defined by the nozzle body 32 and the needle 31, is discommunicated
from the nozzle chamber 35, and the high-pressure gaseous fuel is
not injected into the engine combustion chamber through the
injection holes 37, which are openings of the suction chamber
39.
[0038] The nozzle chamber 35 is formed at a lower half portion of
the nozzle body 32. An outer diameter of the stem portion 312 of
the needle 31 is small, and a diameter of an inner surface 322 of
the nozzle body 32 is large so that a volume capacity of the
high-pressure gaseous fuel in the nozzle chamber 35 is increased.
Specifically, the diameter of the inner surface 322 of the lower
half portion of the nozzle body 32 is larger than a sliding
diameter of the guide portion 311 of the needle 31. The outer
diameter of the stem portion 312 of the needle 31 is smaller than
the largest-diameter part of the generally cone end portion of the
needle 31. In other words, the outer diameter of the stem portion
312 of the needle 31 is formed almost the same as a diameter of the
seating part 38.
[0039] A volume of the high-pressure gaseous fuel at an immediately
upstream space of the injection holes 37 is increased by increasing
a volume of the nozzle chamber 35 inside the nozzle body 32 to
appropriately achieve a flow rate and the pressure of the
high-pressure gaseous fuel at an initial injection. Also, the
high-pressure gaseous fuel is supplied to the nozzle chamber 35
from the injector chamber 43 inside the injector body 5 to inject a
required amount of the high-pressure gaseous fuel without
deteriorating the injection pressure. It is desirable that a volume
of the injector chamber 43 is large enough (e.g., several ones
cm.sup.3) so that the injector 1 accumulates an one-injection
amount of the high-pressure gaseous fuel. The injector chamber 43
is provided on the high-pressure gas passage 41. Other volume
enlarging means may be applied inside the nozzle body 32 or the
injector body 5.
[0040] In the present embodiment, the two feed passages 36a, 36b
are formed in the nozzle body 32 to supply the high-pressure
gaseous fuel to the nozzle chamber 35 from the high-pressure gas
passage 41. The feed passages 36a, 36b are formed at a side of the
guide portion 311 of the needle 31, and open at an upper end
portion of the nozzle chamber 35. A plurality of the feed passages
36a, 36b may be formed to increase the volume of the gaseous fuel
in the nozzle body 32. In other words, two or more of the feed
passages may be formed in order to achieve a sufficient passage
cross sectional area to enlarge the volume of the gaseous fuel in
the nozzle body 32.
[0041] In the present embodiment, the part of the liquid fuel,
which is supplied to control the pressure in the control chamber 2,
is supplied to the nozzle sliding portion to serve as the
lubrication. Also, the small portion of the liquid fuel is injected
into the engine combustion chamber along with the high-pressure
gaseous fuel to serve as the ignition facilitating fuel. Thus, the
liquid fuel, which is supplied as the working fluid, is effectively
used to improve the lubricity and ignitability performance, in
which the gaseous fuel injector may have disadvantages. A structure
of the liquid fuel passage to realize above-described advantages
will be described.
[0042] The gaseous fuel is less lubricant than the liquid fuel.
Thus, the injector may suffer from the wear of the nozzle 3. In the
present embodiment, the second high-pressure liquid passage 34 is
formed beside the guide member 311 of the needle 31, and opens at a
slide hole 321, where the guide member 311 is slidably supported,
to form the first lubrication liquid fuel supply passage. A
plurality of annular grooves 317 is formed at an outer peripheral
of the guide portion 311. The liquid fuel supplied from the second
high-pressure liquid passage 34 lubricates a guide portion 311 and
a slide hole of the nozzle body 32. The liquid, which smoothens the
guide portion 311 and the slide hole of the nozzle body 32, is
pushed above the guide portion 311 by the high-pressure gas in the
nozzle body 32. Then the liquid leaks into the spring chamber 54
inside the injector body 5, flows through the low-pressure liquid
return passage 25, and is recovered through the liquid outlet pipe
26.
[0043] Inside the needle 31, a needle fuel passage (or an
inside-needle fuel passage) 315 is formed in such a manner that an
upper end of the needle fuel passage 315 communicates with an
annular groove 317 (the lowest-positioned annular groove in FIG.
1A) through a communicative hole 316. The needle fuel passage is
also formed in such a manner that a lower end of the needle fuel
passage 315 opens at the lower end portion of the needle 31. A seat
lubrication liquid fuel supply hole 313 and an ignition
facilitating liquid fuel supply hole 314 branch off the needle fuel
passage 315 inside the lower end portion of the needle 31 to open
at the lower end surface of the needle 31. The second high-pressure
liquid passage 34 communicates with the lowest-positioned annular
groove 317, in which the communicative hole 316 is formed, when the
needle 31 is located at the highest position (or a communicating
position) to open the injection holes 37. When the needle 31 opens
the injection holes 37, the high-pressure fuel is led through the
second high-pressure liquid passage 34, the annular groove 317, the
communicative hole 316 and the needle fuel passage 315, and is
supplied to fuel supply holes 313, 314, which are formed at the
lower end portion of the needle 31. The second lubrication liquid
fuel supply passage includes the needle fuel passage 315 and the
seat lubrication liquid fuel supply hole 313. An ignition
facilitating liquid fuel supply passage includes the needle fuel
passage 315 and the ignition facilitating liquid fuel supply hole
314.
[0044] When the needle 31 is located at the closed position for
closing the injection holes 37 as shown in FIG. 1A, the second
high-pressure liquid passage 34 does not communicate with the
annular groove 317. Also, the liquid fuel is not supplied to the
lower end portion of the needle 31 through the needle fuel passage
315. In other words, only when the needle 31 is lifted to open the
injection holes 37, the fuel is supplied to the lower end portion
of the needle 31 through the needle fuel passage 315.
[0045] On an outer peripheral surface of the lower end portion of
the needle 31, a seat annular groove (a circumferential groove) 318
is formed concentrically with an axis of the needle 31 at the
upstream side of the seating part 38 as shown in FIG. 1B. A
plurality of the seat lubrication liquid fuel supply holes 313 open
at the seat annular groove 318. The seat lubrication liquid fuel
supply holes 313 lubricate a downstream side of the seating part 38
by use of the liquid fuel, which is supplied through the second
high-pressure liquid passage 34, the annular groove 317, the
communicative hole 316 and the needle fuel passage 315. The second
high-pressure liquid passage 34 is made communicative with the
annular groove 317 when the injection holes 37 are open. At this
time, the liquid fuel is drawn from the seat lubrication liquid
fuel supply hole 313 by an amount for wetting a surface of the
seating part 38. This is because the gaseous fuel flows slowly at
high pressure around an area where the seat lubrication liquid fuel
supply hole 313 opens. The seat annular groove 318 is formed to
evenly wet the seating part 38 with the liquid fuel. The liquid
fuel spreads entirely along the seat annular groove 318, and is
transferred along a surface of the needle 31 by a flow force of the
high-pressure gaseous fuel, which flows toward the injection holes
37 through the nozzle chamber 35. Then the seating part 38 is
evenly wet.
[0046] Likewise, the seating part 38, which is located at the lower
end of the needle, is lubricated with the liquid fuel, as well as
the guide portion 311 of the needle 31. As a result, the wear of
the sliding portion and the valve portion due to a shortage of the
lubrication is limited. A plurality of the seat lubrication liquid
fuel supply holes 313 may be alternatively formed to effectively
supply the lubricant to the seat annular groove 318. In the present
embodiment, two seat lubrication liquid fuel supply holes 313 are
formed.
[0047] According to the present embodiment, the ignition
facilitating liquid fuel supply hole 314 opens at an immediately
downstream side of the seating part 38, which is located at the
lower end of the needle 31 as shown in FIG. 1B. In this area, the
gaseous fuel flows fast when the needle 31 is lifted to open the
injection holes 37. Thus, the liquid fuel is drawn from the
ignition facilitating liquid fuel supply hole 314 by phenomena of a
spray, and is transferred by the flow force (an energy of a flow)
of the gaseous fuel. Then, mists of the liquid fuel are injected to
the engine combustion chamber through the injection holes 37 along
with the gaseous fuel. At this time, the liquid fuel, which is
supplied through the seat lubricate liquid fuel supply hole 313 at
a previous injection to wet the seating part 38, is detached from
the seating part 38. The liquid fuel is injected into the engine
combustion chamber along with another liquid fuel, which comes from
the ignition facilitating liquid fuel supply hole 314, and the
gaseous fuel.
[0048] Likewise, the liquid fuel, which is injected into the
cylinders, spontaneously ignites in a high-temperature
high-pressure air in the engine combustion chamber to be an
ignition source for the gaseous fuel, which is hard to ignite.
Therefore, a stable combustion is achieved. In the present
embodiment, the ignition facilitating liquid fluid supply hole 314
opens at the immediately downstream of the seating part 38.
However, the ignition facilitating liquid fuel supply hole 314 may
alternatively open at the immediately upstream of the seating part
38.
[0049] As described above, in the present embodiment, the second
high-pressure liquid passage 34 communicates with the common needle
fuel passage 315 by lifting the needle 31 to open the injection
holes 37 to supply the liquid fuel to the guide portion 311. Then,
the liquid fuel is supplied to the seat lubrication liquid fuel
supply hole 313 and the ignition facilitating liquid fuel supply
hole 314 by a predetermined leak amount. A predetermined amount of
the liquid fuel drawn through the seat lubrication liquid fuel
supply hole 313 and the ignition facilitating liquid fuel supply
hole 314 is determined based on the pressure and the flow rate of
the high-pressure gaseous fuel at the open hole area. And the drawn
liquid fuel lubricates the seating part 38, or is injected along
with the gaseous fuel. In the present embodiment, the flow amount
of the liquid fuel is increased by prolonging an opening interval
of the needle 31 to open the injection holes 37, in a case where an
engine load is large. An injection amount of the liquid fuel is set
equal to or less than an amount, which is required to idle the
engine. Thus, the predetermined amount of the liquid fuel is
effectively supplied at every injection. Therefore, both of the
lubrication and the ignition performance are achieved with a simple
passage structure.
(Second Embodiment)
[0050] A second embodiment will be described with reference to
FIGS. 5 and 6. A present invention according to the second
embodiment is different from the invention according to the first
embodiment in the following points. The second high-pressure liquid
passage 34 opens at the annular groove 317 when the needle 31
closes the injection holes 37 (or when the needle 31 is placed in a
communication position). The seat lubrication liquid fuel supply
hole 313 at the lower end portion of the needle 31 is located at
immediately upstream of the seating part 38. The ignition
facilitating liquid fuel supply hole 314 at the lower end portion
of the needle 31 is located at immediately downstream of the
seating part 38. Except for above-mentioned differences, a
structure of a present embodiment is similar to that of the first
embodiment. Similar components of a gaseous fuel injector 1 of the
present embodiment, which are similar to the components of the
injector 1 of the first embodiment, will be indicated by the same
numerals. The second embodiment will be described through focusing
on the differences.
[0051] In the present embodiment, the second high-pressure liquid
passage 34 communicates with the lowest-positioned annular groove
317, when the needle 31 is positioned at the lowest position to
close the injection holes 37 as shown in FIG. 5. The communicative
hole 316 is formed at the lowest-positioned annular groove 317.
When the needle 31 closes the injection holes 37, the annular
groove 317, the communicative hole 316, the needle fuel passage
315, the seat lubrication liquid fuel supply hole 313 and the
ignition facilitating liquid fuel supply hole 314 are filled with
the liquid fuel.
[0052] On the other hand, as shown in FIG. 6, at the outer
peripheral surface of the lower end portion, the seat lubrication
liquid fuel supply hole 313 opens at immediately upstream of the
seating part 38. Also, the ignition facilitating liquid fuel supply
hole 314 opens at immediately downstream of the seating part 38. A
seat annular groove (the circumferential groove) 319a is formed
concentrically with the axis of the needle 31 in such a manner
where an opening of the seat lubrication liquid fuel supply hole
313 is located in the seat annular groove 319a. The seat annular
groove 319a is a slight cavity at an upstream side of the seating
part 38. A seat annular groove (the circumferential groove) 319b is
formed concentrically with the axis of the needle 31 in such a
manner where an opening of the ignition facilitating liquid fuel
supply hole 314 is located in the seat annular groove 319b. The
seat annular groove 319b is the slight cavity at a downstream side
of the seating part 38. The seat lubrication liquid fuel supply
hole 313 and the ignition facilitating liquid fuel supply hole 314
are closed when the needle 31 closes the injection holes 37. This
is realized because the seating part 38 of the needle 31 is
pressingly contacts the seat surface 323 of the nozzle body 32, and
because a difference between cone angles of two cone surfaces 38a,
38b, which are formed at the lower end of the needle 31, is
predetermined to be small.
[0053] Specifically, the cone angle of the cone surface 38b, which
is located in the downstream side of the seating part 38, is larger
than that of the seat surface 323 of the nozzle body 32 by one
degree. Also the cone angle of the cone surface 38a, which is
located in the upstream side of the seating part 38, is smaller
than that of the seat surface 323 of the nozzle body 32 by one
degree. In a case where the cone surface 38 is formed till the
lower end of the needle 31, a passage area to the suction chamber
39 may be decreased due to the cone surface 38b. Therefore, a third
cone surface 38c is formed at the lower end of the needle 31 so
that a passage area to the suction chamber 39 may not be decreased.
A cone angle of the third cone surface 38c is larger than that of
the seat surface 323 of the nozzle body 32 by one degree. In the
present embodiment, a difference between the cone angles of the
third cone surface 38c and the seat surface 323 is 15 degree.
[0054] The seat surface 323 and the cone surfaces 38a, 38b, 38c at
an above-described valve seating part are arranged in such a manner
that the liquid fuel seeps through the seat lubrication liquid fuel
supply hole 313 and the ignition facilitating liquid fuel supply
hole 314 to wet the seat surface 323. The seat annular grooves
319a, 319b, which are slight cavities on the cone surfaces 38a,
38b, are formed in such a manner that the opening of the fuel
supply holes 313, 314 are located in the annular grooves 319a,
319b. Thus, the seat surface 323 is wetted along the whole seat
annular grooves 319a, 319b to improve the lubricity.
[0055] In the above described structure, when the needle 31 opens
the injection holes 37, the liquid fuel is drawn from the seat
lubrication liquid fuel supply hole 313 and the ignition
facilitating liquid fuel supply hole 314 by the flow force of the
gaseous fuel, which flows toward the injection holes 37. Then, the
drawn liquid fuel is transported to the combustion chamber, and
serves as the ignition source similarly to the first embodiment. In
the present embodiment, it is different from the first embodiment
that the annular groove 317 is discommunicated from the second
high-pressure liquid passage 34, when the needle 31 opens the
injection holes 37. When the annular groove 317 is discommunicated,
pressures in the annular groove 317, the communicative hole 316,
the needle fuel passage 315 and the fuel supply hole 313, 314 are
decreased.
[0056] Therefore, an own pressure of the liquid fuel does not push
the liquid fuel itself out of the liquid fuel supply holes 313,
314. Instead, the liquid fuel is drawn out of the liquid fuel
supply holes 313, 314 only by a drawing force of the gaseous fuel.
Thus, the liquid fuel, which is not drawn by the gaseous fuel,
remains at outlets of the liquid fuel supply holes 313, 314 and the
seat annular grooves 319a, 319b.
[0057] The remained liquid fuel limits the wear of the seat surface
323, the seating part 38 of the needle 31 and the cone surfaces
38a, 38b.
[0058] In the present embodiment, a maximum amount of the liquid
fuel injected along with the gaseous fuel is an amount of the fuel,
which fills the annular groove 317, the communicative hole 316, the
needle fuel passage 315, the seat lubrication liquid fuel supply
hole 313, the ignition facilitating liquid fuel supply hole 314 and
the seat annular groove 319a, 319b. Similarly to the first
embodiment, the amount of the drawn liquid fuel depends on the
opening interval of the injection holes 37.
[0059] A supply amount of the liquid fuel for the lubrication of
the seating part is determined independently of a supply amount of
the liquid fuel for facilitating the ignition. The supply amount of
the liquid fuel for facilitating the ignition is set larger than
the supply amount of the liquid fuel for the lubrication of the
seating part.
[0060] According to the present invention, the liquid fuel (or the
working fluid for control the needle) is supplied to the nozzle to
serve as the lubrication or to facilitate the ignition. Therefore,
the lubrication and the ignition control are improved. Therefore,
the wear of the injection nozzle is limited. The wear is a
disadvantage of a cylinder direct injection engine. Also, the
ignition performance is improved to realize a stable combustion. A
poor ignition performance is a disadvantage of a compression
ignition engine. Then, a power of the engine is increased. Also, an
amount of unburned fuel exhaust is decreased.
[0061] In the present embodiment, the liquid fuel is supplied to
the sliding portion of the needle at high pressure. Also at the
same time, a predetermined amount of leak liquid fuel may be
transferred toward the seating part to limit the wear of the
seating part and to facilitate the ignition. Further, the injector
may measure a predetermined amount of the liquid fuel to the
seating part by using a nozzle lift. Also, the communication with a
liquid fuel supply portion may be controlled through an open/close
control by a needle lift. Then, hydrogen gas is limited from
inflowing to the liquid fuel supply portion and the liquid fuel is
limited from excessively outflowing from the liquid fuel supply
portion. Also a back flow of combustion gas is limited. Therefore,
a high-performance injector with a simple structure is
realized.
[0062] Additional advantages and modifications will readily occur
to those skilled in the art. The invention in its broader terms is
therefore not limited to the specific details, representative
apparatus, and illustrative examples shown and described.
* * * * *